I (think) I am looking for a little more flexibility in my 4" I.D. wet exhaust coupler (from riser to hull penetration). I have found a number of 3 and 4 ply silicone hoses with 356F ratings but almost all say: Note: This hose is NOT formulated for use in oil or fuel plumbing applications. It will survive occasional spills and oil leaks, but it will not stand up to continuous exposure to petroleum.
My question, does this include wet exhaust? Anybody successfully (or unsuccessfully use silicone (brand/vendor) for this application?

I can't answer your specific question(s) but I know or a local boat running 4" orange turbo connector sleeves to connect to the tails.

Reason being the orange is rated to 500 degree over blue@ 350ish degrees...and I don't know what the life expectancy on these sleeves are as I didn't ask - but the guy has a boyscout personality where he has 4 spares in the boat, 2 props, 2 blower belts , a distributor with spare MSD, etc... You get the idea

Tom, I am running the "Sheilds" hump exhaust coupler, it is made for exhaust. Mine have been on for 5 years and no problem.
Sounds like you are getting close.

I am concerned that I too have the boy scout mentality...:-)

Thanks...but not much closer, I'm just thinking ahead and still compiling parts.

I've been using this 500°F turbo/intercooler hose for the last 7 years to couple my tails to 4" extensions to exit out my transom.with no issues. I needed a little extra "bend" to get my CMI E-Tops to align with my exhaust holes in my transom

https://www.ebay.com/itm/20351937285...Bk9SR9KZgJi-Yg

I use the high temp silicon (black outside with a red center). Main reason is because after my 496 exhaust has to make a quick "s" turn on the way to the exhaust tips. I used to use the rubber 45 degree elbows but that was one connection after the other because rubber elbows have such short legs. So from the riser it was to a small rubber exhaust tube that connected to a small stright fiberglass tube, to a 45 elbow to another small stright, etc, etc..... Now because of the longer legs (only a couple inches) its, one end of an elbow attached to the riser, the other end attached to a SS pipe to another elbow to the tips. Thats 4 T-bolt clamps per side compared to 8 or 9 before. I will say they are pretty soft and will need to supported. I just used SS tube inside everywhere it didnt actually make a bend and its been fine.

For the price of the sleeves, "T" bolt clamps are must to keep from nicking and cutting into them like a typical hose clamp will readily do

Thanks to everyone above, I am taking it all in 🙂

I have the silicone exhaust couplers on ours. No issues at all and they were recommended becuase of the extra flex as well as they look way better. My builder uses them quite often and has no issues with them.